#include <bits/stdc++.h>
#define ll long long
#define mp make_pair
#define pb push_back
#define mod 1000000007
  
using namespace std;
 
int n, m, a[100100],rs;
int main()
{
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    a[0] = 1, a[1]  = 1;
    cin >> n;
    if (n == 1) return cout << 0 , 0;
    if (n == 2) return cout << 2 , 0;
    int k = 2;
    while (a[k-1] + a[k-2] < n) k++,rs++, a[k] = a[k-1] + a[k-2];
    cout << rs-1;
    return 0;
}